化简sin(a-15度)cos（a+15度）+cos（a-15度)sin(a+15度)

化简sin(a-15度)cos（a+15度）+cos（a-15度)sin(a+15度) 化简~cos^2(a+15)+sin^2(a-15)+sin(a+180)cos(a-180)15为15度 sin(a+105度)cos(a-15度)-cos(a+105度)sin(a-15度) 4.9-1/化简：[cos(a+15度)]^2+[sin(a-15度)]^2+[sin(a+180度)]*[cos(a-180度)].做出来都是1+sin(2a) 化简sin a+cos a 化简cos(45°-a)cos(a+15°)-sin(45°-a)sin(a+15°)的结果为 化简：[cos(a+15度)]^2+[sin(a-15度)]^2+[sin(a+180度)]*[cos(a-180度)].请大家解释一下.[cos(a+15度)]^2+[sin(a-15度)]^2+[sin(a+180度)]*[cos(a-180度)]=[cos(2a+30)+1]/2+[1-cos（2a-30)]/2+1/2sin2a=1+[cos(2a+30)-cos(2a-30)]/2+1/2sin2a=1-2si 化简sin(a+75`)+cos(a+45`)-根号3cos(a+15`) sin(a+105)cos(a-15)-cos(a+105)sin(a-15) sin(a+45°)sin(a+15°)+cos(a+45°)cos(a+15°) 化简tan a(cos a-sin a)+sin a(sin a+tan a)/1+cos a 化简1：cos(15°-a)sin15°-sin(165°+a)cos(-15°)2：根号下cos(60°-a)-sin(60°-a) 化简(sin a^2/cos a +cos a)*cot a 化简:sin(-a)*cos(-a-兀)*tan(2兀+a) sin(180度+a)*cos(-a)/tan(-a) 在三角形abc中,abc为三角形三角,(sin a-sin b)(sin a+sin b)怎么得到sin (a+b)sin (a-b)?另外(30sin 30度)/sin 15度怎么得到60cos 化简:sin(-a)cos(2π+a)sin(-a-π) 化简Sin A + Sin 2A / 1+cos A + cos^4A-sin^4a 化简